John 17:23

I in them, and Thou in Me, that they may be made perfect in one, and that the world may know that Thou hast sent Me, and has loved them as Thou hast loved Me. That their union may be consummated and perfected, as the union of many members in one Body and Head. For, as many members make up one body, so do the many faithful bind together the one mystical Body of Christ, which is His Church. Again, all the members are united and made complete in one head, so are all Christians in One Christ and God. Toletus appositely explains it of the Holy Eucharist; "I am in them," he says, "by My flesh given them as their true and real food, but Thou art in Me, because Thy Godhead is united to My flesh. If therefore the Godhead is in My flesh, and My flesh is in the believers, it comes to pass that the Godhead also is in believers through the medium of the Body of Christ. Believers therefore have in themselves both the Body of Christ, and by means of It the Godhead. They become one, and have through Christ a kind of unity by reason of their flesh, and so are consummated in one, that is, become perfectly one, as not only being united amongst themselves, and with God, as to their souls, which is effected by the Holy Spirit, but also as to their very bodies."

Hence S. Dionysius (De. Divin. Nom. cap. iv.) teaches that Divine Love revolves in a circle, because it comes from God the Father to the Son, and thence to the Holy Spirit, through Whom it returns to the Father and the Son. For the Holy Spirit is the reasonable love of the Father and the Son. Again, it moves in a circle, because it comes from God into the creatures (especially into men and angels), and converts them to the love and enjoyment of God. For as God is the efficient cause of love, so also is He its end. For love transfers him who loves into the beloved object itself. For the soul is really more in that which it loves than in that which it animates. "Therefore S. Paul (Dionysius says), that mighty man, when already led captive by Divine Love, and endued with its strength, which lifts up a man from his own state, says with inspired lips, 'I live, yet not I, but Christ liveth in Me' (Galatians 2:20). And as a true lover, lifted above his own sphere, he lives to God, not his own life, but the life of Him who loves him, as in truth a life which is greatly to be loved." And afterwards he defines love as "a power impelling to action, and attracting upwards to itself, &c., which originates from goodness, and flows from that source of goodness to the things which exist, and thence flows back to goodness. And in this, Divine Love especially shows that It has neither beginning nor end. For it is a perpetual circle, which, springing from a good source (from that which is good) in good deeds, and by turning, back from all which is wrong towards that which is good, sets itself free, and, though abiding in the same spot, is ever advancing, and yet stationary, and comes round on itself."

He then proves it by the authority of his teacher, S. Hierotheus, who says, By love, whether Divine or angelic or spiritual, or so to speak animal or natural, we must understand a force which unites and blends together, which impels those which are superior to consult the good of those who are inferior, which leads those on a level to join in intercourse with each other, and inferiors to look up to superiors. Hence, too, the Egyptians represented God as a circle, but to show rather that He was eternal, without beginning or ending, and accordingly boundless. Whence the saying, "God is a circle, whose centre is everywhere, and whose circumference is nowhere." The Persians also called Jupiter the circle of heaven; and the Saracens too represent God under the same image.

Tropologically. Holy souls strive after perfect union with Christ, forgetting, as it were, everything beside, to keep Him ever before their eyes, to strive in all things to please Him, continually to hold mental converse with Him. And accordingly they withdraw themselves as far as they can from external objects, and hold colloquy with Christ in their hearts. Bartholomew de Martyribus, Archbishop of Braga, in his "Golden Compendium of Spiritual Doctrine," cap. xv., which Louis of Grenada published after his death, and professes that by reading it he profited greatly, as I also say myself, gives three tokens of such inward union:- "(1.) The first is, If the intellect no longer gives utterance to any thoughts save such as the light of faith inspires, and the will, trained by long practice, gives forth no acts of love, except towards God, or with reference to Him. (2.) That as soon as it ceases from any outward employment, in which it is engaged, the understanding and the will are readily turned towards God, just as a stone, when an obstacle is removed, speedily settles down on its point of rest. (3.) If, when prayer is over, it entirely forgets all external objects, as though it had never seen or been engaged in them, and is so disposed towards outward things as though it were now for the first time entering into the world, and feared to engage in external matters, as if naturally shrinking from them, unless charity compelled, such a soul, set free from all outward things, easily withdraws within itself, where only it sees God, and itself in God; and frequently devotes itself to fervid and unitive acts of love. But this fervent love produces, as holy men say, six effects. (1.) Illumination, that is a relishing and experimental knowledge of God, and of its own nothingness. (2.) Warmth. (3.) Sweetness or delight. (4.) An ardent desire to obtain divine blessings. (5.) Satiety, for the mind is so satiated with that coming of God to it, that it wishes or desires nothing further. (6.) Rapture, or a wondrous lifting up of the soul to God, in which it is impossible to explain how it feels towards Him. And two other effects follow, a sense of security, so that the soul fears not any suffering for God's sake, and is fully confident that it will never be separated from Him; and perfect rest, when there is nothing which can inspire fear; and this is called 'the peace which passeth all understanding.' This is the Paradise of God, to which we can ascend, even when living among men in the body." He then sets forth, from S. Thomas, three means of obtaining this union with God and Christ, viz., Boldness, severity, and gentleness of mind. Boldness, to drive away all negligence, and to dispose a man to perform all good works confidently, vigilantly, and methodically. Severity against concupiscence, which brings with it an ardent love of hardness, profiting, and poverty. Gentleness, to expel all rancour, anger, envy, austerity, bitterness, and hardness against one's neighbour. For the soul must first be purged from the dregs of earthly affections, before it is able to ascend simply and purely to God. For as it is the property of fire to ascend, so do souls, when set free from the burden of evil affections, rise up to God, who is their proper resting-place.

And that the world (the faithful in the world) may know that Thou hast sent Me. But how? (1.) In the Beatific Vision, says S. Augustine (in loc.) But then we are here treating of knowledge in this world by faith. (2.) Others say that we shall know by the glory which Christ says above He had received of the Father, and given to the faithful. Whence S. Ambrose (as referred to ver. 22) explains it thus: "The faithful will know that Thou hast sent Me into the world in the flesh, by reason of the Sonship, which I have bestowed on them, in adopting them to be the sons of God. And they will from this know also that Thou hast loved them as Thou hast loved Me: them as my adopted sons, Me as Thy Son by nature." (3.) S. Cyril (xi. 27) and S. Hilary (de Trin. lib. viii.) explain it thus of the Eucharist. They will know thereby two things first, that I am Thy Son, sent by Thee into the world. For they could not be united to us, unless I had the Godhead in that Flesh, which I gave them in the Eucharist; and secondly, that Thou lovedst them, as thou lovedst Me, because Thou gavest to them the Godhead which thou didst unite with My flesh, viz. by giving them My flesh in the Eucharist. (4.) Ribera explains it more simply. The world acknowledges it from the holiness and the mutual charity of the Apostles, by which they were "made perfect in one." For, as S. Chrysostom rightly says, "The Lord judges that concord is more powerful to persuade than miracles." And "Thou hast loved them by making them Apostles, as Thou hast loved Me," begetting Me as Thy Son and in sending Me as Thy ambassador into the world. He thus raises their minds to endure all hardships for Christ's sake.